Double-clutch transmission for vehicles

ABSTRACT

A double-clutch transmission (DCT) includes, but is not limited to an inner input shaft inside an outer input shaft. A first clutch disc and a second clutch disc of the DCT are connected to the two input shafts respectively. Pinions are fixed onto three parallel layshafts of the DCT respectively. The gearwheels on the layshafts include, but are not limited to seven gearwheel groups. Each of the gearwheel group includes, but is not limited to a fixed gearwheel that meshes with an idler gearwheel. A fourth fixed gearwheel on the outer input shaft meshes with the fourth gear idler gearwheel and the sixth gear idler gearwheel. In particular, a fifth fixed gearwheel on the inner input shaft meshes with a fifth gear idler gearwheel and the seventh gear idler gearwheel. The gearwheels further includes, but is not limited to a reverse gearwheel group that includes, but is not limited to a fixed gearwheel on one of the input shafts, meshing with a reverse gear idler gearwheelon one of the layshafts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National-Stage entry under 35 U.S.C. §371 based on International Application No. PCT/EP2009/002305, filed Mar. 31, 2009, which was published under PCT Article 21(2) and which claims priority to European Application No. 08006645.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006638.4, filed Mar. 31, 2008, and which claims priority to European Application No. 08006639.2, filed Mar. 31, 2008, and which claims priority to European Application No. 08006640.0, filed Mar. 31, 2008, and which claims priority to European Application No. 08006641.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006642.6, filed Mar. 31, 2008, and which claims priority to European Application No. 08006635.0, filed Mar. 31, 2008, and which claims priority to European Application No. 08006643.4, filed Mar. 31, 2008, and which claims priority to European Application No. 08006644.2, filed Mar. 31, 2008, and which claims priority to European Application No. 08006486.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006606.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006607.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006608.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006646.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006616.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006617.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006609.5, filed Mar. 31, 2008, and which claims priority to European Application No. 08006610.3, filed Mar. 31, 2008, and which claims priority to European Application No. 08006611.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006612.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006621.0, filed Mar. 31, 2008, and which claims priority to European Application No. 08006622.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006623.6, filed Mar. 31, 2008, and which claims priority to European Application No. 08006624.4, filed Mar. 31, 2008, and which claims priority to European Application No. 08006569.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006637.6, filed Mar. 31, 2008, and which claims priority to European Application No. 08006615.2, filed Mar. 31, 2008, and which claims priority to European Application No. 08006636.8, filed Mar. 31, 2008, and which claims priority to European Application No. 08006625.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006626.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006627.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006628.5, filed Mar. 31, 2008, and which claims priority to European Application No. 08006629.3, filed Mar. 31, 2008, and which claims priority to European Application No. 08006630.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006631.9, filed Mar. 31, 2008, and which claims priority to European Application No. 08006619.4, filed Mar. 31, 2008, and which claims priority to European Application No. 08006620.2, filed Mar. 31, 2008, and which claims priority to European Application No. 08006618.6, filed Mar. 31, 2008, and which claims priority to European Application No. 08006614.5, filed Mar. 31, 2008, and which claims priority to European Application No. 08006613.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006634.3, filed Mar. 31, 2008, and which claims priority to European Application No. 08006633.5, filed Mar. 31, 2008, and which claims priority to European Application No. 08006632.7, filed Mar. 31, 2008, and which claims priority to European Application No. 08006649.1, filed Mar. 31, 2008, and which claims priority to European Application No. 08006648.3, filed Mar. 31, 2008, and which claims priority to European Application No. 08006647.5, filed Mar. 31, 2008, which are all hereby incorporated in their entirety by reference.

TECHNICAL FIELD

The present application relates to a double-clutch transmission for vehicles, such as cars.

BACKGROUND

A double-clutch transmission (DCT) comprises two input shafts that are connected to and actuated by two clutches separately. The two clutches are often combined into a single device that permits actuating any of the two clutches at a time. The two clutches are connected to two input shafts of the DCT separately for providing driving torques.

Volkswagen has presented a DCT named DSG DQ200. The DSG DQ200 is an attempt of having a seven-speed DCT in the cars for street driving. The DCT still has not been widely. Problems that hinder the wide application of DCT comprise of providing a compact, reliable and fuel-efficient DCT. Therefore, there exists a need for providing such a DCT that is also affordable by consumers.

SUMMARY

The present application provides a double-clutch transmission (DCT) that comprises an inner input shaft and an outer input shaft. The inner input shaft is partially inside the outer input shaft. In other words, the outer input shaft encloses the inner input shaft in a radial direction. The radial direction indicates regions that surround a longitudinal axis of the inner input shaft.

The DCT has a first clutch disc that is non-rotatably connected to the inner input shaft. The DCT also has a second clutch disc that is non-rotatably connected to the outer input shaft. The non-rotatable connections ensure that a connection between two joined shafts causes simultaneous rotation of the two shafts. For example, the two shafts can be fused together to make the non-rotatable connection. Alternatively, the non-rotatable connection can be provided by a universal joint.

There are a first layshaft, a second layshaft and a third layshaft radially spaced apart from the input shafts. These layshafts are arranged in parallel to the input shafts. Longitudinal axes of these shafts are parallel to each other, including overlapping. One or more of the layshafts comprise a pinion for outputting a drive torque to a drive train of a vehicle. The drive train can alternatively be referred as powertrain or powerplant that comprises the group of components for generating power and delivering it to the road surface, water, or air. The drive train can include an engine, a transmission, drive shafts, differentials, and final drive. The final drive can be drive wheels, continuous track like with tanks or caterpillar tractors, propeller, etc. Sometimes “drive train” refers simply to the engine and the transmission, including the other components only if they are integral to the transmission.

Gearwheels of the DCT are arranged on the three layshafts and on the input shafts. These gearwheels comprise a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group, a sixth gearwheel group and a seventh gearwheel group for providing seven sequentially increasing gears. The sequentially increasing gears describe an escalating order that members of the order follow each other. Gears of a car can be arranged in a sequentially increasing manner from first gear to seventh gear. For example, in a car having a DCT, a first gear has a gear ratio of 2.97:1; a second gear has a gear ratio of 2.07:1; a third gear has a gear ratio of 1.43:1; a fourth gear has a gear ratio of 1.00:1; a fifth gear has a gear ratio of 0.84:1; a sixth gear has a gear ratio of 0.56:1; and a seventh gear has a gear ratio of 0.42:1. The seven gears provide an increasing order of output speed of the transmission for driving the car.

The first gearwheel group comprises a first fixed gearwheel on the inner input shaft that meshes with a first gear idler gearwheel on one of the layshafts. The third gearwheel group comprises a third driving gearwheel on the inner input shaft that meshes with a third driven gearwheel on one of the layshafts. The driving gearwheel can be a gearwheel fixed on its carrying shaft or an idler gearwheel that is free to rotate around its carrying shaft. Similarly, the driven gearwheel can also be a gearwheel fixed on its carrying shaft or an idler gearwheel that is free to rotate around its carrying shaft. A carrying shaft of a gearwheel is a shaft that is mounted with the gearwheel for carrying the weight and transmits torque of the gearwheel.

The fifth gearwheel group comprises a fifth fixed gearwheel on the inner input shaft that meshes with a fifth gear idler gearwheel on one of the layshafts. The seventh gearwheel group comprises a seventh fixed gearwheel on the inner input shaft that meshes with a seventh gear idler gearwheel on one of the layshafts. The second gearwheel group comprises a second fixed gearwheel on the outer input shafts that meshes with a second gear idler gearwheel on one of the layshafts. The fourth gearwheel group comprises a fourth fixed gearwheel on the outer input shafts that meshes with a fourth gear idler gearwheel on one of the layshafts. The sixth gearwheel group comprises a sixth fixed gearwheel on the outer input shafts that meshes with a sixth gear idler gearwheel on one of the layshafts.

Each gearwheel group comprises a coupling device that is arranged on one of the layshafts to selectively engage one of the gearwheels to one of the layshafts for selecting one of the seven gears. The fourth fixed gearwheel meshes with both the fourth gear idler gearwheel and the sixth gear idler gearwheel.

Especially, the fifth fixed gearwheel meshes with both the fifth gear idler gearwheel and the seventh gear idler gearwheel. The gearwheels of the DCT further comprise a reverse gearwheel group that comprises a fixed gearwheel on one of the input shafts. The fixed gearwheel of the reverse gearwheel group meshes with a reverse gear idler gearwheel on one of the layshafts. The reverse gearwheel group further comprises a coupling device that is arranged on the layshaft mounted with the reverse gear idler gearwheel to selectively engage the reverse gear idler gearwheel.

The DCT provides seven forward gears through a dual clutch. The DCT makes gear switching between odd and even ratios to be swift and efficient because the gearwheels of the odd and even gears are driven by different clutch discs respectively. One double meshing feature is provided by the fourth fixed gearwheel that meshes with the fourth gear idler gearwheel and the sixth gear idler gearwheel. Another double meshing feature is provided by the fifth fixed gearwheel that meshes with the fifth gear idler gearwheel and the seventh gear idler gearwheel. The two double meshing features make the DCT to be compact and lightweight at low cost because two fixed gearwheels are avoided on the input shafts.

The double clutch transmission can provide two coupling devices that engage two of the idler gearwheels of the seven gears respectively at the same time. The process of multiple engagements of the two idler gearwheels on different layshafts is known as pre-selection of gears. Especially, the two idlers of two consecutive gears that are driven by different input shafts of the DCT can be both engaged for shifting from one of the two gears to the other. For example, idler gearwheels of the third gear and the fourth gear of the DCT are both engaged to their weight-carrying layshaft by their neighbouring coupling devices when only one of the input shafts receives an input torque. Since incoming torque from any of the input shafts is constantly delivered to an idler gearwheel of the two consecutive gears, there is little or no interruption in torque flow during the gearshift. Therefore, the double-clutch transmission provides continuous and more efficient torque transmission, as compared to the gearshift process in Manual Transmissions.

In the application, the DCT can further comprise a second reverse gearwheel group that comprises a fixed gearwheel on one of the input shafts that meshes with a second reverse gear idler gearwheel on one of the layshafts. The meshing can be provided directly between the two gearwheels or indirectly via other gearwheels. The second reverse gearwheel group can further comprise a coupling device which is arranged on the layshaft mounted with the second reverse gear idler gearwheel to selectively engage the second reverse gear idler gearwheel for proving a second reverse gear. The second reverse gear can be driven by one of the input shafts that is different from the other reverse gear. The second reverse gear enables dual speeds for reversing a vehicle, which can be useful driving different applications of a multi-purpose vehicle. For example, the first reverse gear can be used as a faster reverse operation, whilst the second reverse gear can be used as a slower and silent reverse operation, or vice versa.

According to the application, different input shafts can provide the first forward gear and the second reverse gear. The DCT can put the first forward gear and the second reverse gear on two different input shafts. Dual clutches of the DCT enables that the switching between the two input shafts can be achieved quickly. As a result, a driving scheme that the DCT engages the two input shafts alternatively can drive the vehicle back & forth rapidly. This scheme is useful for moving the vehicle out of a muddy puddle because the vehicle can simply be driven back & forth to get out the puddle. Less loss of momentum of the gearwheels and the layshafts of the DCT can be achieved. Alternatively, the back and forth movements can be provided by a second forward gear and a first reverse gear on different input shafts.

The reverse gearwheel group can provide a second reverse gear, in addition to the previously mentioned first gear. One of the two reverse gears provides a powerful and slower reverse gear. In contrast, the other reverse gear provides a faster reverse gear with less strength. The two reverse gears at different speeds enable some special vehicles, such as a Leopard II Main Battle Tank, to increase their maneuverability and operation efficiency.

The two reverse gears can be driven by different input shafts. This scheme makes the interchange between the two reverse gears to be fast, just by alternatively engaging one of the two clutches of the DCT.

In the application, the DCT can comprise a reverse gear idler shaft or a reverse gear layshaft, a reverse gearwheel and a reverse pinion. The reverse gearwheel and the reverse pinion can be both mounted on the reverse gear idler shaft or the or the reverse gear layshaft. Distance of reverse torque transmission has been reduced by arranging the reverse gearwheel and the reverse pinion on the same shaft. The reverse gear thus has improved transmission efficiency.

The double-clutch transmission can further comprise a park-lock gearwheel that is fixed onto one of the layshafts for providing a park-lock. The layshaft with the park-lock comprises a final drive pinion for engaging and locking a differential of the DCT. The differential comprises the output gearwheel on the output shaft. The park-lock enables a vehicle with the park-lock to park at a place in a secure manner, even on a slope. The park-lock is easy to implement and beneficial for the vehicle and passengers' safety.

In the application, the DCT can comprise two pinions mounted on two of the layshafts respectively, instead of the one pinion. The two pinions on the layshafts can mesh or comb with one relatively big output gearwheel on an output shaft. The output gearwheel can be integrated into a transmission differential device without providing an intermediate output shaft of the transmission gearbox. This allows a very dense packaging situation for the DCT.

According to the application, the first gear idler gearwheel can be provided on one of the layshafts. In contrast, the fourth idler gearwheel, the fifth idler gearwheel, the sixth idler gearwheel and the seventh idler gearwheel can be provided on the remaining layshafts.

According to application, two or more of the second gear idler gearwheel, the third driven gearwheel, the fourth gear idler gearwheel and the fifth gear idler gearwheel can be mounted on the same layshaft. Putting idler gearwheels of high gears on the same shaft can make their weight and torque carrying layshaft to be slim for low cost.

In the application, the sixth gear idler gearwheel and the seventh gear idler gearwheel can be mounted on the same layshaft. In a sever-gear DCT, idlers of the six and seventh gears carry the least torques so that their weight and torque carrying layshaft can be made very slim for light weight and low cost.

In the application, the DCT comprises bearings for supporting the layshafts. One or more of the bearings can be provided next to some or all of the pinions. The pinion that outputs torque of its carrying layshaft is better supported by immediately adjacent bearing for reducing the deflection and load the layshaft. The supporting bearing thus can improve torque transmission efficiency and reduce cost of the DCT.

According to the application, one or more of the bearings can be provided next to one of the idler gearwheels of low gears. Gearwheels of low gears transmit larger torques as compared to the gearwheels of high gears. Close support of the bearings help to reduce excessive deflection and weight related cost of their carrying shafts.

According to the application, there can be gearbox that comprises the DCT and an output gearwheel on an output shaft. The output gearwheel can mesh with each of the pinions. The output gearwheel provides a single source of torque output so that the construction of the DCT is made simple and neat.

In the application, there can be a power train device with the gearbox. The power train device can comprise one or more power source for generating a driving torque. The power train device usually has the gearbox and the power source onboard so that a vehicle with the power train device can be mobile without being physically attached to an external stationary power source.

In the application, the power source can comprise a combustion engine. The power train with the combustion engine and the DCT is easy to manufacture. The combustion engine can consume less petrol for environmental protection. Furthermore, a combustion engine usable for other types of fuel can have even less polluting emission, such as hydrogen fuel.

According to the application, the power source can alternatively comprises an electric motor. Electric motor used in a hybrid car, or in an electrical car enables reduction of pollution, as compared to typical combustion using petrol. The electric motor can even recuperate brake energy in a generator mode.

According to the application, there can be a vehicle that comprises the power train device. The vehicle having the power train device is efficient in energy usage by using the DCT.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and

FIG. 1 illustrates a front view of a first embodiment of a double clutch transmission of the application;

FIG. 2 illustrates the path of torque flow of a first gear transmission ratio;

FIG. 3 illustrates the path of torque flow of a second gear transmission ratio;

FIG. 4 illustrates the path of torque flow of a third gear transmission ratio;

FIG. 5 illustrates the path of torque flow of a fourth gear transmission ratio,

FIG. 6 illustrates the path of torque flow of a fifth gear transmission ratio;

FIG. 7 illustrates the path of torque flow of a sixth gear transmission ratio;

FIG. 8 illustrates the path of torque flow of a seventh gear transmission ratio;

FIG. 9 illustrates the path of torque flow of a first reverse gear transmission ratio;

FIG. 10 illustrates the path of torque flow of a second reverse gear transmission ratio;

FIG. 11 illustrates an assembly of a double-sided coupling device with its neighbouring gearwheels for engagement;

FIG. 12 illustrates an assembly of a single-sided coupling device with its neighbouring gearwheel for engagement;

FIG. 13 illustrates an assembly of an idler gearwheel that is rotatably supported by a shaft on a bearing;

FIG. 14 illustrates an assembly of a fixed gearwheel that is supported on a shaft;

FIG. 15 illustrates a cross-section through a crankshaft of an internal combustion engine according to embodiment of the DCT;

FIG. 16 illustrates a front view of a further embodiment of a double clutch transmission of the application;

FIG. 17 illustrates an expanded side view of the double clutch transmission of FIG. 16;

FIG. 18 illustrates a front view of a further embodiment of a double clutch transmission of the application;

FIG. 19 illustrates an expanded side view of the double clutch transmission of FIG. 18;

FIG. 20 illustrates a front view of a further embodiment of a double clutch transmission of the application;

FIG. 21 illustrates an expanded side view of the double clutch transmission of FIG. 20;

FIG. 22 illustrates a front view of a further embodiment of a double clutch transmission of the application; and

FIG. 23 illustrates an expanded side view of the double clutch transmission of FIG. 22.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature and is not intended to limit application and uses. Furthermore, there is no intention to be bound by any theory presented in the preceding background or summary or the following detailed description.

In the following description, details are provided to describe the embodiments of the application. It shall be apparent to one skilled in the art, however, that the embodiments may be practised without such details.

FIGS. 1-15 provide detailed description of an embodiment of a double clutch transmission (DCT) of the application.

FIG. 1 illustrates a front view of an embodiment of a double clutch transmission 1 of the application. The DCT 1 comprises a relatively large output gearwheel 12, an upper idler layshaft 40, two input shafts 20, 22 and two pinions 51, 55. The two input shafts 20, 22 are a solid input shaft 20 (i.e. K1) and a hollow input shaft 22 (i.e. K2). The solid input shaft 20 and the hollow input shaft 22 share the same rotational axis and are non-rotatably connected to two clutch discs 8, 10 of a double clutch 6, separately. The two pinions are the lower pinion 51 and the reverse pinion 55. The two pinions are fixed to a lower layshaft 50 and a reverse gear layshaft 38 at their rotational axes respectively. The output gearwheel 12 is fixed to an output shaft 14 at its rotation axis. The two pinions mesh with the output gearwheel 12 separately at different positions of the output gearwheel 12.

The upper idler layshaft 40, the lower layshaft 50, the input shafts 20, 22, and the reverse gear layshaft 38 are parallel to each other at predetermined distances. The distances are provided in radial directions of these shafts, which is better seen in FIG. 2. Other gearwheels are mounted on these shafts respectively meshing with each other according to predetermined manners. The manners of these gearwheels' mounting and meshing are better seen in some of the following figures.

FIG. 1 further shows a cutting plane A-A for illustrating an expanded cross-section view through the DCT 1, which is shown in FIGS. 2 to 9. The cutting plane A-A passes through the rotational axes of the output gearwheel 12, the reverse pinion 55, the input shafts 20, 22, the lower pinion 51 and the upper idler layshaft 40. One of the goals of FIGS. 2 to 9 is to further illustrate structure and torque flows of the DCT 1.

FIG. 2 illustrates the expanded view of the DCT that shows the manners of the gearwheels mounting, which corresponds to FIG. 1.

According to FIG. 2, the DCT 1 comprises the following shafts, from top to bottom, the upper idler layshaft 40, the lower layshaft 50, the hollow input shaft 22, the solid input shaft 20, the reverse gear layshaft 38 and the output shaft 14. The solid input shaft 20 is partially disposed inside the hollow input shaft 22, and the solid input shaft 20 also protrudes outside the hollow input shaft 22 at its two ends. The hollow input shaft 22 is mounted onto the solid input shaft 20 by a pair of solid shaft bearings 71 that are disposed between the solid input shaft 20 and the hollow input shaft 22 at two ends of the hollow input shaft 22. As a result, the two input shafts 20, 22 are coupled together such that the solid input shaft 20 is free to rotate inside the hollow input shaft 22. The hollow input shaft 22 surrounds a right portion of the solid input shaft 20, and a left portion of the solid input shaft 20 is exposed outside the hollow input shaft 22. The assembly of the input shafts 20, 22 is supported by a solid shaft bearing 71 at a protruding end of the solid shaft 20 on the left and by a hollow shaft bearing 72 on the hollow input shaft 22 on the right.

According to FIG. 2, a portion of the solid input shaft 20 is surrounded by the outer input shaft 22 in a radial direction of the input shafts 20, 22. There are three gearwheels and a coupling device mounted on the left exposed portion of the solid input shaft 20. These gearwheels and the coupling device are a fixed wheel fifth gear 26, a single-sided coupling device 85, an idler wheel third gear 25 and a fixed wheel first gear 24 from left to right sequentially. The fixed wheel fifth gear 26 also serves as a fixed wheel seventh gear 27. All of the fixed wheel first gear 24, the idler wheel third gear 25 and the fixed wheel fifth gear 26 are fixed onto the solid input shaft 20 coaxially. On the hollow input shaft 22, which is mounted on the right portion of the solid input shaft 20, there are attached with a fixed wheel second gear 30 and a fixed wheel fourth gear 31 from right to left. The fixed wheel fourth gear 31 also serves as a fixed wheel sixth gear 32. Both the fixed wheel second gear 30 and the fixed wheel fourth gear 31 are fixed to the hollow input shaft 22 coaxially.

The lower layshaft 50 is provided above the solid input shaft 20 and the hollow input shaft 22. There are a number of gearwheels and coupling devices mounted on the lower layshaft 50, which include, from right to the left, the lower pinion 51, an idler fourth gear 63, a single-sided coupling device 82, a park-lock gearwheel 39, an idler third gear 62, a double-sided coupling device 81 and an idler fifth gear 64. One layshaft bearing 73 is provided between the lower pinion 51 and the idler fourth gear 63. Another layshaft bearing 73 is provided next to the idler fifth gear 64 at the left end of the lower layshaft 50. The lower pinion 51 is fixed onto the lower layshaft 50 at its rotational axis. The idler fourth gear 63, the idler third gear 62 and the idler fifth gear 64 are mounted on the lower layshaft 50 by bearings separately such that these gearwheels become idlers, being free to rotate around the lower layshaft 50. In contrast, the park-lock gearwheel 39 is a gear wheel that is fixed onto the lower layshaft 50. The double-sided coupling devices 81 is configured to move along the lower layshaft 50 such that it can either engage a gearwheel on its left or right to the lower layshaft 50 respectively. The single-sided coupling device 82 is configured to move along the lower layshaft 50 to engage or disengage the idler fourth gear 63. The idler fourth gear 63 meshes with the fixed wheel fourth gear 31. The idler third gear 62 meshes with the idler wheel third gear 25. The idler fifth gear 64 meshes with the fixed wheel fifth gear 26.

The upper idler layshaft 40 is provided further above the lower layshaft 50. There are provided gearwheels and coupling devices on the upper idler layshaft 40, which includes, from right to the left, an idler second gear 61, a single-sided coupling device 86, a single-sided coupling device 80, an idler first gear 60 and a fixed wheel auxiliary gear 28. One idler shaft bearing 74 is positioned at a left end of the upper idler layshaft 40 and another idler shaft bearing 74 is positioned at right end of the upper idler layshaft 40. The idler second gear 61 and the idler first gear 60 are mounted on the upper idler layshaft 40 by bearings respectively such that these gearwheels are free to rotate around the upper idler layshaft 40. The fixed wheel auxiliary gear 28 is fixed onto the upper idler layshaft 40. The single-sided coupling device 80 is configured to move along the upper idler layshaft 40 to engage or disengage the idler first gear 60 to the upper idler layshaft 40. The single-sided coupling device 86 is configured to move along the upper idler layshaft 40 to engage or disengage the idler second gear 61 to the upper idler layshaft 40. The idler second gear 61 meshes with the fixed wheel second gear 30. The idler first gear 60 meshes with the fixed wheel first gear 24. The fixed wheel auxiliary gear 28 meshes with the idler wheel third gear 25.

The reverse gear layshaft 38 is provided below the input shafts 20, 22. There are gearwheels and coupling devices provided on the reverse gear layshaft 38, which includes, from right to the left, the reverse pinion 55, an idler sixth gear 65, a single-sided coupling device 84, a reverse gear idler wheel 37, a double-sided coupling device 83 and an idler seventh gear 66. The idler sixth gear 65, the reverse gear idler wheel 37 and the idler seventh gear 66 are mounted on the reverse gear layshaft 38 via bearings separately such that these gearwheels become idlers, being able to freely rotate around the reverse gear layshaft 38. A layshaft bearing 73 is positioned between the reverse pinion 55 and the idler sixth gear 65. Another layshaft bearing 73 is positioned at a left end of the reverse gear layshaft 38. The single-sided coupling device 84 is configured to move along the reverse gear layshaft 38 for engaging or disengaging the idler sixth gear 65 to the reverse gear layshaft 38. The double-sided coupling device 83 is configured to move along the reverse gear layshaft 38 for engaging or disengaging any one of the reverse gear idler wheel 37 and the idler seventh gear 66 to the reverse gear layshaft 38. The idler sixth gear 65 meshes with the fixed wheel sixth gear 32. The reverse gear idler wheel 37 meshes with the idler first gear 60. The idler seventh gear 66 meshes with the fixed wheel seventh gear 27.

The lower layshaft 50 comprises a fixed park-lock gearwheel 39 for locking the upper layshaft 50 when parking a vehicle with the double-clutch transmission 1. The park-lock is a wheel which is provided with a ratchet device, with a click device having a rack element, a claw or similar. The park-lock keeps the lower layshaft 50 and the output shaft 14 from rotating, which stops a vehicle with the DCT 1 from running when parked. When using the park-lock, the park-lock gearwheel 39 on the lower layshaft 40 can be easily engaged to lock the output shaft 14, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, and stopping the output shaft 14 from rotating. The lower pinion 51 is a final drive pinion, which is similar to the reverse pinion 55. Detailed structure of the park-lock is not shown in FIG. 2.

In other words, there are three double-meshing features provided in the DCT 1. A first double-meshing feature comprises that the fixed wheel fourth gear 31 meshes with both the idler fourth gear 63 and the idler sixth gear 65. A second double meshing feature comprises that the fixed wheel fifth gear 26 meshes with both the idler fifth gear 64 and the idler seventh gear 66. A third double-meshing feature comprises that the idler first gear 60 meshes with both the fixed wheel first gear 24 and the reverse gear idler wheel 37.

A distance 56 between the input shafts 20, 22 and the upper idler layshaft 40 is greater than a distance 58 between the input shafts 20, 22 and the lower 30 layshaft 50. The distance 56 between the input shafts 20, 22 and the upper idler layshaft 40 is measured from a common longitudinal axis of the input shafts 20, 22 to a longitudinal axis of the upper idler layshaft 40. Similarly, the distance 58 between the input shafts 20, 22 and the lower layshafts 50 is measured from the common longitudinal axis of the input shafts 20, 22 to a longitudinal axis of the lower layshaft 50. The difference exists because the gearwheels of lower speeds 60, 61 on the upper idler layshaft 40 is larger than the gearwheels 62, 63, 64 on the lower layshaft 50 so that the upper idler layshaft 40 is brought to be closer to the input shafts 20, 22 than the lower layshaft 50.

The output shaft 14 is provided below the reverse gear layshaft 38 in FIG. 2. Two output shaft bearings 75 at two opposite ends of the output shaft 14 respectively for supporting. The output gearwheel 12 is mounted on the output shaft 14 coaxially. The output gearwheel 12 is also fixed on the output shaft 14 and meshes with the lower pinion 51.

In the present specification, the expressions “mesh” and “comb” with respect to geared wheels or engaged gearwheels are provided as synonyms. The solid input shaft 20 is alternatively termed as an inner input shaft 20, while the hollow input shaft 22 is alternatively termed as an outer input shaft 22. The solid input shaft 20 is alternatively replaced by a hollow shaft and disposed inside the hollow input shaft 22. The term “coupling device” is alternatively termed as “shifting mechanism” for engaging or disengaging gearwheels on a shaft. The double-clutch transmission (DCT) 1 is alternatively termed as double-clutch, double clutch transmission or dual clutch transmission (DCT). The inner clutch disc 8 also known as an inner clutch 8. The outer clutch disc 10 is additionally known as an outer clutch 10.

The fixed wheel first gear 24 is also known as the first fixed gearwheel 24. The idler wheel third gear 25 is also known as the third idler gearwheel 25. The fixed wheel fifth gear 26 is also known as the fifth fixed gearwheel 26. The fixed wheel seventh gear 27 is also known as the seventh fixed gearwheel 27. The fixed wheel auxiliary gear 28 is also known as the auxiliary fixed gearwheel 28. The fixed wheel second gear 30 is also known the second fixed gearwheel 30. The fixed wheel fourth gear 31 is also known as the fourth fixed gearwheel 31. The fixed wheel sixth gear 32 is also known as the sixth fixed gearwheel 32. The reverse gear idler wheel 37 is also known as the reverse gear idler gearwheel 37. The idler first gear 60 is also known as the first gear idler gearwheel 60. The idler second gear 61 is also known as the second gear idler gearwheel 61. The idler third gear 62 is also known as the third gear idler gearwheel 62. The idler fourth gear 63 is also known as the fourth gear idler gearwheel 63. The idler fifth gear 64 is also known as the fifth gear idler gearwheel 64. The idler sixth gear 65 is also known as the sixth gear idler gearwheel 65. The idler seventh gear 66 is also known as the seventh gear idler gearwheel 66. The coupling devices are alternatively known as synchronizers. Any of the input shafts 20, 22 or layshafts 38, 40, 50 can be supported by more than two bearings.

In the drawings of the present application, dash lines indicate either alternative positions of the illustrated parts or combing relationship between the gearwheels.

The application provides the DCT 1 that permits gearshift operations with less loss of driving torque. This is because the gearshift operations can be achieved by selectively connecting one of the two clutch discs 8, 10 of the DCT 1. Therefore, an associated additional main drive clutch can be avoided. Selective connections between the two clutch discs 8, 10 also enable the realization of an automatic transmission that can be operated without interruptions in propulsive power. The propulsive power comprises momentum derived from the rotating gearwheels and shafts inside the DCT 1. Such a transmission is similar in design to a mechanical manual transmission and it has correspondingly very low friction losses. The DCT 1 further provides a parallel manual transmission that can be used for transverse installation in a front-wheel drive vehicle.

The DCT 1 according to the application can be connected similar to a known manual transmission, such as a parallel manual transmission. In the know manual transmission, a drive shaft for the front axle of a vehicle extends outward from its DCT case, and parallel to the output shaft 14 of the main DCT 1. The arrangement of the known manual transmission provides little space left for actuation of the manual transmission and clutch, and also for an optional electric motor. The optional electric motor can act as a starter device for a combustion engine, as an energy recuperation device for brake operation or as an additional drive means in hybrid vehicles. Having such little space presents a number of difficulties that are solved or at least alleviated by the application. The application provides a DCT 1 that has two clutches for connecting to an electrical motor and the manual transmission in a compact manner.

The application provides a compact structure of a parallel transmission. The parallel transmission includes two input shafts, each of which can be non-rotatably coupled via its own clutch to a shaft that is powered by a drive engine of a vehicle. The DCT 1 of the application further provides the output shaft 14 that is parallel to the input shafts 20, 22.

The DCT 1 according to the application is particularly well suited for transverse installation in front-wheel drive vehicles, in which the front differential, for example, is positioned below the pinions 51, 55. A short overall length of the power train for transmitting torques can be achieved.

The application provides at least two relatively small pinions 51, 55 on intermediately arranged layshafts 50, 38 that comb with one relatively big output gearwheel 12. The output gearwheel 12 in turn is fixed onto the output shaft 14. This arrangement provides a compact and lightweight DCT 1.

The application further allows a design in which the output gearwheel 12 is integrated into a transmission differential device without providing an intermediate output shaft of the DCT 1. This allows a very dense packaging situation for the DCT 1.

It is further not only of advantage to provide fixed wheels for the even gearwheels on one input shaft and fixed gearwheels for the odd gears on another input shaft. This arrangement provides the above-mentioned power-shift operation in a smooth and efficient manner when gearshift is performed sequentially. This is because the DCT 1 can alternatively engage one of the two clutch discs 8, 10 in the process of increasing or decreasing gears. For example, the power-shift operation from the first gear to the fourth gear causes the solid input shaft 20 and the hollow input shaft 22 being engaged alternatively, which is energy efficient and fast.

Some gearwheels of the low gears (e.g. 1st & 2nd gears) provided on the same layshaft are advantageous. In FIG. 2, the idler first gear 60 and the idler second gear 61 are installed on the same upper idler layshaft 40. Furthermore, the idler third gear 62, the idler fourth gear 63 and the idler fifth gear 64 are installed on the same upper layshaft 50. This arrangement enables one thick lower layshaft for carrying a number of heavy-duty gearwheels 62, 63, 64, and avoids providing too many thick layshafts in the DCT 1. Therefore, the DCT 1 can be made light with less cost.

The layshaft bearings 73 of the DCT 1 are next to the pinions 51, 55. The layshaft bearings 73 offer strong support to the pinion carrying layshafts 50, 38 for reducing shaft deflection, which can lower gear transmission efficiency or cause gearwheels early worn out. The idler shaft bearing 74 next to the idler second gear 61 also provide strong support to the idler second gear 61 and the upper idler layshaft 40.

In other words, it is beneficial to provide the gearwheels of the first gear, of the second gear and of the pinions 51, 55 close to the bearings for supporting. The pinions 51, 55 and gearwheels of these gearwheels of low gears (e.g. 2nd gear, 4th gear etc) undergo bigger forces than those of the higher gears because the drive ratio is larger for the lower gears and reverse gears. Therefore, their shafts must take up stronger driving forces. If those forces are taken up close to the support points of the shafts a reduced shaft bending will occur.

FIG. 2 illustrates the path of torque flow of a first gear transmission ratio. In FIG. 2, an input torque of the first gear is received from a crankshaft 2 of a combustion engine (not shown). According to FIG. 2, the input torque of the first gear is received by the solid input shaft 20 from the double-clutch 6 of the DCT 1. A torque of the first gear is transmitted from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the single-sided coupling device 80, via the upper idler layshaft 40, via the fixed wheel auxiliary gear 28, via the idler wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 81, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14. The single-sided coupling device 80 is engaged to the idler first gear 60 when transmitting the torque of the first gear, which provides the first gear of the DCT 1. The double-sided coupling device 81 is engaged to the idler third gear 62 when transmitting the first gear. The number of tooth engagements or engaged gear pairs for the torque transfer of the first gear is four.

FIG. 3 illustrates the path of torque flow of a second gear transmission ratio. In FIG. 3, an input torque of the second gear is received from the crankshaft 2 of the combustion engine (not shown). According to FIG. 3, the input torque of the second gear is received by the hollow input shaft 22 from the double-clutch 6 of the DCT 1. A torque of the second gear is transmitted from the hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, via the single-sided coupling device 86, via the upper idler layshaft 40, via the fixed wheel auxiliary gear 28, via the idler wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 81, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14. The single-sided coupling device 86 is engaged to the idler second gear 61 when transmitting the torque of the second gear, which provides the second gear of the DCT 1. The double-sided coupling device 81 is engaged to the idler third gear 62 when transmitting the second gear. The number of tooth engagements or engaged gear pairs for the torque transfer of the second gear is four.

FIG. 4 illustrates the path of torque flow of a third gear transmission ratio. In FIG. 4, an input torque of the third gear is received from the crankshaft 2 of the combustion engine (not shown). According to FIG. 4, the input torque of the third gear is received by the solid input shaft 20 from the double-clutch of the DCT 1. A torque of the third gear is transmitted from the solid input shaft 20, via the single-sided coupling device 85, via the idler wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 81, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 81 is engaged to the idler third gear 62 when transmitting the torque of the third gear, which provides the third gear of the DCT 1. The single-sided coupling device 85 is engaged to the idler wheel third gear 25 when transmitting the third gear. The number of tooth engagements or engaged gear pairs for the torque transfer of the third gear is two.

FIG. 5 illustrates the path of torque flow of a fourth gear transmission ratio. In FIG. 5, an input torque of the fourth gear is received from the crankshaft 2 of the combustion engine (not shown). According to FIG. 5, the input torque of the fourth gear is received by the hollow input shaft 22 from the double-clutch 6 of the DCT 1. A torque of the fourth gear is transmitted from the hollow input shaft 22, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the single-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14. The single-sided coupling device 82 is engaged to the idler fourth gear 63 when transmitting the torque of the fourth gear, which provides the fourth gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the fourth gear is two.

FIG. 6 illustrates the path of torque flow of a fifth gear transmission ratio. In FIG. 6, an input torque of the fifth gear is received from the crankshaft 2 of a combustion engine (not shown). According to FIG. 6, the input torque of the fifth gear is received by the solid input shaft 20 from the double-clutch 6 of the DCT 1. A torque of the fifth gear is transmitted from the solid input shaft 20, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the double-sided coupling device 81, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 81 is engaged to the idler fifth gear 64 when transmitting the torque of the fifth gear, which provides the fifth gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the fifth gear is two.

FIG. 7 illustrates the path of torque flow of a sixth gear transmission ratio. In FIG. 7, an input torque of the sixth gear is received from the crankshaft 2 of a combustion engine (not shown). According to FIG. 7, the input torque of the sixth gear is received by the hollow input shaft 22 from the double-clutch 6 of the DCT 1. A torque of the sixth gear is transmitted from the hollow input shaft 22, via the fixed wheel sixth gear 32, via the idler sixth gear 65, via the single-sided coupling device 84, via the reverse gear layshaft 38, via the reverse pinion 55, via the output gearwheel 12, to the output shaft 14. The single-sided coupling device 84 is engaged to the idler sixth gear 65 when transmitting the torque of the sixth gear, which provides the sixth gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the sixth gear is two.

FIG. 8 illustrates the path of torque flow of a seventh gear transmission ratio. In FIG. 8, an input torque of the seventh gear is received from the crankshaft 2 of a combustion engine (not shown). According to FIG. 8, the input torque of the seventh gear is received by the solid input shaft 20 from the double-clutch 6 of the DCT 1. A torque of the seventh gear is transmitted from the solid input shaft 20, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 83, via the reverse gear layshaft 38, via the reverse pinion 55, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 83 is engaged to the idler seventh gear 66 when transmitting the torque of the seventh gear, which provides the seventh gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the seventh gear is two.

FIG. 9 illustrates the path of torque flow of a first reverse gear transmission ratio. In FIG. 9, an input torque of the reverse gear is received from the crankshaft 2 of a combustion engine (not shown). According to FIG. 9, the input torque of the first reverse gear is received by the solid input shaft 20 from the double-clutch 6 of the DCT 1. A torque of the reverse gear is transmitted from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the reverse gear idler wheel 37, via the double-sided coupling device 83, via the reverse gear layshaft 38, via the reverse pinion 55, via the output gearwheel 12, to the output shaft 14. The double-sided coupling device 83 is engaged to the reverse gear idler wheel 37 when transmitting the torque of the reverse gear, which provides the reverse gear of the DCT 1. The number of tooth engagements or engaged gear pairs for the torque transfer of the reverse gear is three.

FIG. 10 illustrates the path of torque flow of a second reverse gear transmission ratio. In FIG. 9, an input torque of the second reverse gear is received from the crankshaft 2 of a combustion engine (not shown). According to FIG. 9, the input torque of the second reverse gear is received by the hollow input shaft 22 from the double-clutch 6 of the DCT 1. A torque of the second reverse gear is transmitted from the hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, via the single-sided coupling device 86, via the upper idler layshaft 40, via the single-sided coupling device 80, via the idler first gear 60, via the reverse gear idler wheel 37, via the double-sided coupling device 83, via the reverse gear layshaft 38, via the reverse pinion 55, via the output gearwheel 12, to the output shaft 14. When transmitting the torque of the second reverse gear, the single-sided coupling device 86 engages the idler second gear 61 to the upper idler layshaft 40, the single-sided coupling device 80 engages the idler first gear 60 to the upper idler layshaft 40, and the double-sided coupling device 83 engages the reverse gear idler wheel 37 to the reverse gear layshaft 38. The number of tooth engagements or engaged gear pairs for the torque transfer of the reverse gear is four.

FIG. 11 illustrates an assembly 100 of a double-sided coupling device 102 with its neighbouring gearwheels 101, 103 for engagement. The assembly 100 comprises a shaft 104 with the two coaxially mounted idler gear 101, 103 on two bearings respectively. The coupling device 102 is provided between the idler gear 101 on the left and the idler gear 103 on the right. The coupling device 102 is configured to move along the shaft 104 to selectively engage any of the idler gears 101, 103 at one time. In other words, the idler gears 101, 103 can alternatively be brought into non-rotating engagement with the shaft 104 by the coupling device 102. Symbols for showing the assembly 100 is provided at the right hand side of FIG. 11.

FIG. 12 illustrates an assembly 110 of a single-sided coupling device 112 with its neighbouring gearwheel 113 for engagement. The assembly 110 comprises a shaft 114 with the one coaxially mounted idler gear 113 on a bearing. The coupling device 112 is provided next to the idler gear 113 on the left side. The coupling device 112 is configured to move along the shaft 114 to engage or disengage the idler gears 113. In other words, the idler gear 113 can be brought into non-rotating engagement with the shaft 114 by the single-sided coupling device 112. Symbols for showing the assembly 110 are provided at the right hand side of FIG. 12.

FIG. 13 illustrates an assembly 120 of an idler gearwheel 121 that is rotatably supported by a shaft 122 on a bearing 123. The idler gearwheel 121 is coaxially mounted onto the shaft 122 via the bearing 123. The bearing 123 enables the idler gearwheel 121 to be freely rotated around the shaft 122. Symbols that represent the assembly 120 are provided at the right hand side of the FIG. 13.

FIG. 14 illustrates an assembly 130 of a fixed gearwheel 132 that is supported on a shaft 131. The fixed gearwheel 132 is coaxially mounted onto the shaft 131 such that the gearwheel 132 is fixed to the shaft 132. The fixed gearwheel 132 and the shaft 131 are joined as one single body such that torque of the fixed gearwheel 132 is transmitted to the shaft 131 directly, and vice versa.

A number of fixed gearwheels are rigidly connected to the input shafts 20, 22 and other shafts 14, 38, 40, 50. A symbol as used in the previous figures for such a fixed gearwheel is provided on the left side in FIG. 14. The more commonly used symbol for such a fixed gearwheel is provided on the right side in FIG. 14.

FIG. 15 illustrates a cross-section through a crankshaft 2 of an internal combustion engine according to the embodiment of the DCT 1. According to FIG. 15, a crankshaft 2 of an internal combustion engine, which is not shown here, is non-rotatably connected to the housing 4 of a double clutch 6. The double clutch 6 includes an inner clutch disc 8 and an outer clutch disc 10, which can be brought into non-rotating engagement with the housing 4 via control elements that are not illustrated here. The solid input shaft 20 is non-rotatably connected to the clutch disc 8, and extends all the way through the hollow shaft 22. Similarly, the hollow input shaft 22 is non-rotatably connected to the other clutch disc 10.

The clutch housing 4 has a larger outer diameter around the inner clutch disc 8 than that around the outer clutch disc 10. Correspondingly, the inner clutch disc 8 has a larger outer diameter than that of the outer clutch disc 10 inside the clutch housing 4. The fact that the larger inner clutch disc 8 on the solid input shaft 20 drives the first gear makes the DCT 1 robust.

The above-mentioned nine torque flow paths not only provide viable solutions to generate nine gears of the DCT 1, but also offer possibilities of switching from one gear to the another efficiently. The gear switching can be achieved by switching between the two input shafts, between gearwheels of double meshing features, or both.

For example, the DCT 1 can provide odd gears (i.e. 1st, 3rd, 5th & 7th gears) by driving the gearwheels of the DCT 1 using the solid input shaft 20. Alternatively, the DCT 1 can provide even gears (i.e. 2nd, 4th & 6th gears) by driving the gearwheels of the DCT 1 using the hollow input shaft 22. Gear switching between the odd and even can simply be obtained by alternating between the two input shafts 20, 22.

One double meshing feature provides efficient and fast gear switching between gears of two driven gearwheels that comb with a shared driving gearwheel. For example, the DCT 1 provides the convenience of selecting the fourth gear or the sixth gear without stopping their shared driving gearwheel, the fixed wheel fourth gear 31. The selection can be achieved by engaging either the driven idler fourth gear 63 or the driven idler sixth gear 65. Similarly, the gear switching between the fifth gear and the seventh gear can be simply engaging any one of the running gearwheels, namely the idler fifth gear 64 and the idler seventh gear 66.

Combining the switching technique between the input shafts 20, 22 or between the driven gearwheels of one double meshing, flexibility of gear changes can be further enhanced. For example, the gear switching from the fourth to the seventh can be provided by disengaging the hollow input shaft 22, followed by engaging the solid input shaft 20 and the idler seventh gear 66.

The double-meshing features reduce the number of driving gearwheels, which is commonly engaged by driven gearwheels of their double-meshing feature. For example, the driving fixed wheel fourth gear 31 and the driving fixed wheel sixth gear 32 become one single gearwheel that is shared by the driven idler fourth gear 63 and the driven idler sixth gear 65. The driving fixed wheel fifth gear 26 and the driving fixed wheel seventh gear 27 become one single gearwheel that is shared by the driven idler fifth gear 64 and the driven idler seventh gear 66. As a result, the number of gearwheels on the input shafts 20, 22 has been reduced and less space is required on the input shafts 20, 22 so that the DCT 1 can be made cheaper and lighter.

The park-lock gearwheel 39 gives an useful safety feature for a car with the DCT 1. The park-lock keeps the lower layshaft 50, the output shaft 14 and the output shaft 14 from rotating, which stop a vehicle with the DCT 1 from running when parked.

In providing gear meshing or combing for torque transmission, less number of gear tooth engagement (i.e. gear engagement) is preferred. The less number of gear tooth engagement provides lower noise and more efficient torque transmission.

The DCT 1 drives the gearwheel groups of the first gear and the second reverse gear by different input shafts 20, 22. This provides the ability to drive a vehicle change between a slow forward and a slow backward by engaging and disengaging the respective clutches 8, 10 that are connected to the two input shafts 20, 22. The DCT 1 enables the vehicle to move back and forth quickly with little loss of the transmission power or gearwheels momentum by using the first gear and the second reverse gear for that operation. This helps in many situations in which a wheel of a vehicle with the DCT 1 is stuck in a hostile environment such as a snow hole or a mud hole. The vehicle can then be swayed free just by switching between the two clutch discs 8, 10 of the DCT 1. Alternatively, the vehicle can change between the second gear and the first reverse gear to move back and forth quickly by alternatively engaging between the inner input shaft and the outer input shaft.

FIGS. 16-17 illustrate a further embodiment of the application. The embodiment includes parts that are similar to the parts of previously described embodiment. The similar parts are labelled with the same or similar part reference number. Descriptions related to the similar parts are hereby incorporated by reference.

FIG. 16 illustrates a front view of a further embodiment of a double clutch transmission 1 of the application. A relatively big output gearwheel 12 meshes with a lower pinion 51 which is provided on a lower layshaft 50. The output gearwheel 12 further meshes with an upper pinion 41 which is provided on an upper layshaft 40. In some variants of the application, at least one a further layshaft with a further pinion can be provided but this is not shown here. Such a further pinion would then also mesh or comb with the output gearwheel 12.

FIG. 16 further comprises a cutting plane A-A for illustrating the cross-section through the gearbox which is shown in FIG. 17. For an embodiment which has more than two layshafts or an additional idler shaft, a cutting plane which leads through all shafts is applied similarly. One of the goals of FIG. 17 is to further illustrate the structure and the torque flows through the embodiment of the gearbox 1.

FIG. 17 illustrates an expanded side view of the double clutch transmission 1 of FIG. 16. The expanded side view illustrates structure and various torque flows for the several gears of the double clutch transmission gearbox 1. The double clutch transmission gearbox 1 comprises the following shafts, from top to bottom, a top layshaft 90, the upper layshaft 40, a solid input shaft 20, a hollow shaft 22, and the lower layshaft 50. The above-mentioned shafts are provided parallel to each other at predetermined mutual distances inside the gearbox 1. The hollow shaft 22 is arranged concentrically around the solid shaft 20. The solid input shaft 20 protrudes outside the hollow input shaft 22 at a right end.

The solid input shaft 20 comprises, from the right end to the left end, a solid shaft bearing 71, a hollow shaft bearing 72, which serves also as a solid shaft bearing 71, a fixed wheel first gear 24, an idler third gear 62, a single-sided coupling device 86, and a fixed wheel fifth gear 26, which is at the same time a fixed wheel seventh gear 27, and a solid shaft bearing 71.

The hollow input shaft 22 comprises, from the right end to the left end, a hollow shaft bearing 72, a fixed wheel second gear 30, and a fixed wheel fourth gear 28, which serves also as a fixed wheel sixth gear 29.

The upper layshaft 40 comprises, from the right end to the left end, the upper pinion 41, a layshaft bearing 73, an idler fourth gear 63, combing with the fixed wheel fourth gear 28, a single-sided coupling device 80, a park-lock gearwheel 39, a fixed wheel third gear 25, combing with the idler third gear 62, a single-sided coupling device 81, an idler fifth gear 64, combing with the fixed wheel fifth gear 26, and a layshaft bearing 73.

The top layshaft 90 comprises, from the right end to the left end, a layshaft bearing 73, an idler second gear 61, combing with the fixed wheel second gear 30, a single-sided coupling device 84, a single-sided coupling device 87, an idler first gear 60, combing with the fixed wheel first gear 24, a fixed top wheel 92, combing with the idler third gear 62, and a layshaft bearing 73.

The lower layshaft 50 comprises, from the right end to the left, a lower pinion 51, an idler shaft bearing 74, an idler sixth gear 65, combing with the fixed wheel sixth gear 29, a single-sided coupling device 83, a reverse gear idler wheel 37, combing with the idler first gear 60, a double-sided coupling device 82, an idler seventh gear 66, combing with the fixed wheel seventh gear 27, and an idler shaft bearing 74.

Torque flow of the first gear according to FIG. 17, starts from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the single-sided coupling device 84, via the top layshaft 90, via the fixed top wheel 92, via the idler third gear 62, via the fixed wheel third gear 25, via the upper layshaft 40, and to the upper pinion 41.

Torque flow of the second gear according to FIG. 17 starts from the hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, via the single-sided coupling device 84, via the top layshaft 90, via the fixed top wheel 92, via the idler third gear 62, via the fixed wheel third gear 25, via the upper layshaft 40, to the upper pinion 41.

Torque flow of the third gear according to FIG. 17 starts from the solid input shaft 20, via the single-sided coupling device 86, via the idler third gear 62, via the fixed wheel third gear 25, via the upper layshaft 40, to the upper pinion 41.

Torque flow of the fourth gear according to FIG. 17 starts from the hollow input shaft 22, via the fixed wheel fourth gear 28, via the single-sided coupling device 80, via the upper layshaft 40, to the upper pinion 41.

Torque flow of the fifth gear according to FIG. 17 starts from the solid input shaft 20, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the single-sided coupling device 81, via the upper layshaft 40, to the upper pinion 41.

Torque flow of the sixth gear according to FIG. 17 starts from the hollow input shaft 22, via the fixed wheel sixth gear 29, via the idler sixth gear 65, via the single-sided coupling device 83, via the lower layshaft, to the lower pinion 51.

Torque flow of the seventh gear according to FIG. 17 starts from the solid input shaft 20, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 82, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the first reverse gear according to FIG. 17 starts from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the reverse gear idler wheel 37, via the double-sided coupling device 82, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the second reverse gear according to FIG. 17 starts from the hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, via the single-sided coupling device 84, via the top layshaft 90, via the single-sided coupling device 87, via the idler first gear 60, via the reverse gear idler wheel 37, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, via the output gearwheel 12, to the output shaft 14.

FIGS. 18-19 illustrate a further embodiment of the application. The embodiment includes parts that are similar to the parts of previously described embodiments. The similar parts are labelled with the same or similar part reference number. Descriptions related to the similar parts are hereby incorporated by reference.

FIG. 18 shows a front view of the gearbox 1 of the application. A relatively big output gearwheel 12 meshes with a lower pinion 51 which is provided on a lower layshaft 50. The output gearwheel 12 further meshes with a reverse pinion 55 which is provided on a reverse gear shaft 38. In some variants of the application, at least one a further layshaft with a further pinion can be provided but this is not shown here. Such a further pinion would then also mesh or comb with the output gearwheel 12.

FIG. 18 further comprises a cutting plane A-A for illustrating the cross-section through the gearbox which is shown in FIG. 19. For an embodiment which has more than two layshafts or an additional idler shaft, a cutting plane which leads through all shafts is applied similarly. One of the goals of FIG. 19 is to further illustrate the structure and the torque flows through the embodiment of the gearbox 1.

FIG. 19 illustrates a simplified cross-section through the double clutch transmission gearbox 1 of FIG. 18. It illustrates structure and various torque flows for the several gears of the double clutch transmission gearbox 1. The double clutch transmission gearbox 1 comprises the following shafts, from top to bottom, the upper layshaft 40, the lower layshaft 50, the solid input shaft 20, the hollow shaft 22, and the reverse gear shaft 38.

The above-mentioned shafts are provided parallel to each other at predetermined mutual distances inside the gearbox 1. The hollow shaft 22 is arranged concentrically around the solid shaft 20. The solid input shaft 20 protrudes outside the hollow input shaft 22 at a right end.

The solid input shaft 20 comprises, from the right end to the left end, a solid shaft bearing 71, a hollow shaft bearing 72, which serves also as a solid shaft bearing 71, a fixed wheel first gear 24, an idler third gear 62, a single-sided coupling device 82, a fixed wheel fifth gear 26, which is at the same time a fixed wheel seventh gear 27, and a solid shaft bearing 71.

The hollow input shaft 22 comprises, from the right end to the left end, a hollow shaft bearing 72, a fixed wheel second gear 30, and a fixed wheel fourth gear 31, which serves also as a fixed wheel sixth gear 32.

The upper layshaft 40 comprises, from the right end to the left end, a layshaft bearing 73, an idler second gear 61, combing with the fixed wheel second gear 30, a single-sided coupling device 86, a single-sided coupling device 84, an idler first gear 60, combing with the fixed wheel first gear 24, a fixed wheel third gear 28, combing with the idler third gear 62, and a layshaft bearing 73.

The reverse gear shaft 38 comprises, from the right end to the left end, the reverse pinion 55, an idler shaft bearing 74, an idler sixth gear 65, combing with the fixed wheel sixth gear 32, a double-sided coupling device 83, a reverse gear idler wheel 37, combing with the idler first gear 60, a single-sided coupling device 85, an idler seventh gear 66, combing with the fixed wheel seventh gear 27, and an idler shaft bearing 74.

The lower layshaft 50 comprises, from the right end to the left end, the lower pinion 51, a layshaft bearing 73, an idler fourth gear 63, combing with the fixed wheel fourth gear 31, a single-sided coupling device 80, a park-lock gearwheel 39, a fixed wheel third gear 25, combing with the idler third gear 62, a single-sided coupling device 81, an idler fifth gear 64, combing with the fixed wheel fifth gear 26, and a layshaft bearing 73.

Torque flow of the first gear according to FIG. 19 starts from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the single-sided coupling device 84, via the upper layshaft 40, via the fixed wheel third gear 28, via the idler third gear 62, via the fixed wheel third gear 25, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the second gear according to FIG. 19 starts from hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, via the single-sided coupling device 86, via the upper layshaft 40, via the fixed wheel third gear 28, via the idler third gear 62, via the fixed wheel third gear 25, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the third gear according to FIG. 19 starts from the solid input shaft 20, via the double-sided coupling device 82, via the idler third gear 62, via the fixed wheel third gear 25, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the fourth gear according to FIG. 19 starts from hollow input shaft 22, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the single-sided coupling device 80, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the fifth gear according to FIG. 19 starts from solid input shaft 20, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the single-sided coupling device 81, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the sixth gear according to FIG. 19 starts from the hollow input shaft 22, via the fixed wheel sixth gear 32, via the idler sixth gear 65, via the double-sided coupling device 83, via the reverse gear shaft 38, to the reverse pinion 55.

Torque flow of the seventh gear according to FIG. 19 starts from the solid input shaft 20, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the single-sided coupling device 85, via the reverse gear shaft 38, to the reverse pinion 55.

Torque flow of the first reverse gear according to FIG. 19 starts from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the reverse gear idler wheel 37, via the double-sided coupling device 83, via the reverse gear shaft 38, to the reverse pinion 55.

Torque flow of the second reverse gear according to FIG. 19 starts from the hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, via the single-sided coupling device 86, via the upper layshaft 40, via the single-sided coupling device 84, via the idler first gear 60, via the reverse gear idler wheel 37, via the double-sided coupling device 83, via the reverse gear shaft 38, to the reverse pinion 55, via the output gearwheel 12, to the output shaft 14.

FIGS. 20-21 illustrate a further embodiment of the application. The embodiment includes parts that are similar to the parts of previously described embodiments. The similar parts are labelled with the same or similar part reference number. Descriptions related to the similar parts are hereby incorporated by reference.

FIG. 20 shows a front view of the gearbox of the application. A relatively big output gearwheel 12 meshes with a lower pinion 51 which is provided on a lower layshaft 50. The output gearwheel 12 further meshes with a reverse pinion 55, which is provided on a reverse gear shaft 38. In some variants of the application, at least one a further layshaft with a further pinion can be provided but this is not shown here. Such a further pinion would then also mesh or comb with the output gearwheel 12.

FIG. 20 further comprises a cutting plane A-A for illustrating the cross-section through the gearbox which is shown in FIG. 21. For an embodiment which has more than two layshafts or an additional idler shaft, a cutting plane which leads through all shafts is applied similarly. One of the goals of FIG. 21 is to further illustrate the structure and the torque flows through the embodiment of the gearbox.

FIG. 21 illustrates a simplified cross-section through the double clutch transmission gearbox 1 of FIG. 20. They illustrate its structure and various torque flows for the several gears of the double clutch transmission gearbox 1.

The double clutch transmission gearbox 1 comprises the following shafts, from top to bottom, an upper layshaft 40, the lower layshaft 50, the solid input shaft 20, the hollow shaft 22, and the reverse gear shaft 38. The above-mentioned shafts are provided parallel to each other at predetermined mutual distances inside the gearbox 1. The hollow shaft 22 is arranged concentrically around the solid shaft 20. The solid input shaft 20 protrudes outside the hollow input shaft 22 at a right end.

The solid input shaft 20 comprises, from the right end to the left end, a solid shaft bearing 71, a hollow shaft bearing 72, which serves also as a solid shaft bearing 71, a fixed wheel first gear 24, an idler third gear 62, a single-sided coupling device 84, a fixed wheel fifth gear 26, which is at the same time a fixed wheel seventh gear 27, and a solid shaft bearing 71.

The hollow input shaft 22 comprises, from the right end to the left end, a hollow shaft bearing 72, a fixed wheel reverse gear 35, a fixed wheel fourth gear 31, which serves also as a fixed wheel sixth gear 32, and a fixed wheel second gear 30.

The upper layshaft 40 comprises, from the right end to the left end, an idler shaft bearing 74, an idler reverse gear 67, combing with the fixed wheel reverse gear 35, a single-sided coupling device 86, a single-sided coupling device 85, an idler first gear 60, combing with the fixed wheel first gear 24, a fixed wheel third gear 28, combing with the idler third gear 62, and an idler shaft bearing 74.

The reverse gear shaft 38 comprises, from the right end to the left end, a reverse pinion 55, a layshaft bearing 73, an idler sixth gear 65, combing with the fixed wheel sixth gear 32, a double-sided coupling device 83, a reverse gear idler wheel 37, combing with the idler first gear 60, a double-sided coupling device 82, an idler seventh gear 66, combing with the fixed wheel seventh gear 27, and an idler shaft bearing 74.

The lower layshaft 50 comprises, from the right end to the left end, the lower pinion 51, a layshaft bearing 73, an idler fourth gear 63, combing with the fixed wheel fourth gear 31, a double-sided coupling device 80, an idler second gear 61, combing with the fixed wheel second gear 30, a park-lock gearwheel 39, a fixed wheel third gear 25, combing with the idler third gear 62, a single-sided coupling device 81, an idler fifth gear 64, combing with the fixed wheel fifth gear 26, and a layshaft bearing 73.

Torque flow of the first gear according to FIG. 21 starts from solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the single-sided coupling device 85, via the upper layshaft 40, via the fixed wheel third gear 28, via the idler third gear 62, via the fixed wheel third gear 25, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the second gear according to FIG. 21 starts from hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, via the double-sided coupling device 80, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the third gear according to FIG. 21 starts from solid input shaft 20, via the single-sided coupling device 84, via the idler third gear 62, via the fixed wheel third gear 25, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the fourth gear according to FIG. 21 starts from the hollow input shaft 22, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the double-sided coupling device 80, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the fifth gear according to FIG. 21 starts from the solid input shaft 20, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the single-sided coupling device 81, via the lower layshaft 50, to the lower pinion 51.

Torque flow of the sixth gear according to FIG. 21 starts from the hollow input shaft 22, via the fixed wheel sixth gear 32, via the idler sixth gear 65, via the double-sided coupling device 83, via the reverse gear shaft 38, to the reverse pinion 55.

Torque flow of the seventh gear according to FIG. 21 starts from the solid input shaft 20, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 82, via the reverse gear shaft 38, to the reverse pinion 55.

Torque flow of the first reverse gear according to FIG. 21 starts from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the reverse gear idler wheel 37, via the double-sided coupling device 83, via the reverse gear shaft 38, to the reverse pinion 55.

Torque flow of the second reverse gear according to FIG. 21 starts from the hollow input shaft 22, via the fixed wheel reverse gear 35, via the idler reverse gear 67, via the single-sided coupling device 86, via the upper layshaft 40, via the single-sided coupling device 85, via the idler first gear 60, via the reverse gear idler wheel 37, via the double-sided coupling device 83, via the reverse gear shaft 38, to the reverse pinion 55.

FIGS. 22-23 illustrate a further embodiment of the application. The embodiment includes parts that are similar to the parts of previously described embodiments. The similar parts are labelled with the same or similar part reference number. Descriptions related to the similar parts are hereby incorporated by reference.

FIG. 22 shows a front view of the gearbox of the application. A relatively big output gearwheel 12 on an output shaft 14 meshes with a lower pinion 51 which is provided on a lower layshaft 50. The output gearwheel 12 further meshes with an upper pinion 41, which is provided on an upper layshaft 40. A reverse gear idler shaft 38 carries a number of gearwheels that meshes with gearwheels on the upper layshaft 40 and input shafts 20, 22 according to a predetermined manner. The input shafts 20, 22, the upper layshaft 40 and the lower layshaft 50 are parallel to each other, and the two input shafts 20, 22 are coaxial. In some variants of the application, at least one a further layshaft with a further pinion can be provided but this is not shown here. Such a further pinion would then also mesh or comb with the output gearwheel 12.

FIG. 22 further comprises a cutting plane A-A for illustrating the cross-section through the gearbox which is shown in FIG. 23. For an embodiment which has more than two layshafts or an additional idler shaft, a cutting plane which leads through all shafts is applied similarly. One of the goals of FIG. 23 is to further illustrate the structure and the torque flows through the embodiment of the gearbox.

FIG. 23 illustrates a simplified cross-section through the double clutch transmission gearbox 1 of FIG. 22. They illustrate its structure and various torque flows for the several gears of the double clutch transmission gearbox 1.

The double clutch transmission gearbox 1 comprises the following shafts, from top to bottom, the reverse gear idler shaft 38, an upper layshaft 40, the hollow shaft 22, the solid input shaft 20, the lower layshaft 50, and the output shaft 14. The above-mentioned shafts are provided parallel to each other at predetermined mutual distances inside the gearbox 1. The hollow shaft 22 is arranged concentrically around the solid shaft 20. The solid input shaft 20 protrudes outside the hollow input shaft 22 at a right end.

The solid input shaft 20 comprises, from the right end to the left end, a solid shaft bearing 71, a hollow shaft bearing 72, which serves also as a solid shaft bearing 71, a fixed wheel fifth gear 26, which also serves as a fixed wheel seventh gear 27, a fixed wheel third gear 25, a fixed wheel first gear 24, and a solid shaft bearing 71.

The hollow input shaft 22 comprises, from the right end to the left end, a hollow shaft bearing 72, a fixed wheel second gear 30, which also serves as a fixed wheel third reverse gear 34, a fixed wheel fourth gear 31, which serves also as a fixed wheel sixth gear 32, a hollow shaft bearing 72, which also serves as a solid shaft bearing 71.

The upper layshaft 40 comprises, from the right end to the left end, the upper pinion 41, a layshaft bearing 73, an idler reverse gear 37, a double-sided coupling device 80, an idler fourth gear 63 meshing with the fixed wheel fourth gear 31, an idler fifth gear 64 meshing with the fixed wheel fifth gear 26, a double-sided coupling device 81, an idler third gear 62 meshing with the fixed wheel third gear 25, a park-lock gearwheel 39, and a layshaft bearing 73.

The reverse gear idler shaft 38 comprises, from the right end to the left end, an idler shaft bearing 74, a fixed wheel first reverse gear 35, a fixed wheel second reverse gear 36, and an idler shaft bearing 74. The fixed wheel first reverse gear 35 meshes with the fixed wheel third reverse gear 34. The fixed wheel second reverse gear 36 meshes with the idler reverse gear 37.

The lower layshaft 50 comprises, from the right end to the left end, the lower pinion 51, a layshaft bearing 73, an idler second gear 61 combing with the fixed wheel second gear 30, a double-sided coupling device 83, an idler sixth gear 65 combing with the fixed wheel sixth gear 32, an idler seventh gear 66 combing with the fixed wheel seventh gear 27, a double-sided coupling device 82, an idler first gear 60 combing with the fixed wheel first gear 24, and a layshaft bearing 73.

Torque flow of the first gear according to FIG. 23 starts from the solid input shaft 20, via the fixed wheel first gear 24, via the idler first gear 60, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, via the output gear wheel 12, to the output shaft 14.

Torque flow of the second gear according to FIG. 23 starts from the hollow input shaft 22, via the fixed wheel second gear 30, via the idler second gear 61, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, via the output gear wheel 12, to the output shaft 14.

Torque flow of the third gear according to FIG. 23 starts from the solid input shaft 20, via the fixed wheel third gear 25, via the idler third gear 62, via the double-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, via the output gear wheel 12, to the output shaft 14.

Torque flow of the fourth gear according to FIG. 23 starts from the hollow input shaft 22, via the fixed wheel fourth gear 31, via the idler fourth gear 63, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, via the output gear wheel 12, to the output shaft 14.

Torque flow of the fifth gear according to FIG. 23 starts from the solid input shaft 20, via the fixed wheel fifth gear 26, via the idler fifth gear 64, via the double-sided coupling device 81, via the upper layshaft 40, via the upper pinion 41, via the output gear wheel 12, to the output shaft 14.

Torque flow of the sixth gear according to FIG. 23 starts from the hollow input shaft 22, via the fixed wheel sixth gear 32, via the idler sixth gear 65, via the double-sided coupling device 83, via the lower layshaft 50, via the lower pinion 51, via the output gear wheel 12, to the output shaft 14.

Torque flow of the seventh gear according to FIG. 23 starts from the solid input shaft 20, via the fixed wheel seventh gear 27, via the idler seventh gear 66, via the double-sided coupling device 82, via the lower layshaft 50, via the lower pinion 51, via the output gear wheel 12, to the output shaft 14.

Torque flow of the reverse gear according to FIG. 23 starts from the hollow input shaft 22, via the fixed wheel third reverse gear 34, via the fixed wheel first reverse gear 35, via the reverse gear idler shaft 38, via the fixed wheel second reverse gear 36, via the idler reverse gear 37, via the double-sided coupling device 80, via the upper layshaft 40, via the upper pinion 41, via the output gear wheel 12, to the output shaft 14.

Although the above description contains much specificity, these should not be construed as limiting the scope of the embodiments but merely providing illustration of the foreseeable embodiments. Especially the above stated advantages of the embodiments should not be construed as limiting the scope of the embodiments but merely to explain possible achievements if the described embodiments are put into practise. Thus, the scope of the embodiments should be determined by the claims, rather than by the examples given.

While at least one exemplary embodiment has been presented in the foregoing summary and detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration in any way. Rather, the foregoing summary and detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope as set forth in the appended claims and their legal equivalents. 

1. A double-clutch transmission, comprising: an inner input shaft and an outer input shaft, at least a portion of the inner input shaft surrounded by the outer input shaft; a first clutch connected to the inner input shaft and a second clutch connected to the outer input shaft; a first layshaft, a second layshaft and a third layshaft spaced apart from the input shafts and arranged in parallel to the input shafts; at least one of the layshafts comprising a pinion for outputting a drive torque; gearwheels arranged on the first layshaft, on the second layshaft, on the third layshaft, on the inner input shaft and on the outer input shaft, the gearwheels comprising a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group, a sixth gearwheel group and a seventh gearwheel group for providing seven sequentially increasing gears, the first gearwheel group comprising a first fixed gearwheel on the inner input shaft, meshing with a first gear idler gearwheel on one of the layshafts, the third gearwheel group comprising a third driving gearwheel on the inner input shaft, meshing with a third driven gearwheel on one of the layshafts, the fifth gearwheel group comprising a fifth fixed gearwheel on the inner input shaft, meshing with a fifth gear idler gearwheel on one of the layshafts, the seventh gearwheel group comprising a seventh fixed gearwheel on the inner input shaft, meshing with a seventh gear idler gearwheel on one of the layshafts, the second gearwheel group comprising a second fixed gearwheel on the outer input shafts, meshing with a second gear idler gearwheel on one of the layshafts, the fourth gearwheel group comprising a fourth fixed gearwheel on the outer input shafts, meshing with a fourth gear idler gearwheel on one of the layshafts, the sixth gearwheel group comprising a sixth fixed gearwheel on the outer input shafts, meshing with a sixth gear idler gearwheel on one of the layshafts, and each gearwheel group comprising a coupling device which is arranged on one of the layshafts to selectively engage one of the gearwheels for selecting one of the seven gears, and the fourth fixed gearwheel further meshing with the sixth gear idler gearwheel, wherein the fifth fixed gearwheel further meshes with the seventh gear idler gearwheel, and the gearwheels further comprises a reverse gearwheel group that comprises a fixed gearwheel on one of the input shafts, meshing with a reverse gear idler gearwheel on one of the layshafts for providing a reverse gear, and the reverse gearwheel group further comprises a coupling device which is arranged on the layshaft mounted with the reverse gear idler gearwheel to selectively engage the reverse gear idler gearwheel.
 2. The double-clutch transmission device according to claim 1, further comprising: the first forward gear and the reverse gear are provided by different input shafts.
 3. The double-clutch transmission according to claim 1, wherein the reverse gearwheel group provides a first reverse gear and a second reverse gear.
 4. The double-clutch transmission device according to claim 1, further comprising a reverse gear shaft, a reverse gearwheel and a reverse pinion, the reverse gearwheel and the reverse pinion mounted on the reverse gear shaft.
 5. The double-clutch transmission device according to claim 1, further comprising a park-lock.
 6. The double-clutch transmission device according to claim 1, wherein the first gear idler gearwheel is provided on one of the layshafts while the fourth idler gearwheel, the fifth idler gearwheel, the sixth idler gearwheel and the seventh idler gearwheel are provided on the remaining layshafts.
 7. The double-clutch transmission according to claim 1, wherein at least two of the second gear idler gearwheel, the third driven gearwheel, the fourth gear idler gearwheel and the fifth gear idler gearwheel are mounted on the same layshaft.
 8. The double-clutch transmission according to claim 1, wherein the sixth gear idler gearwheel and the seventh gear idler gearwheel are mounted on the same layshaft.
 9. The double-clutch transmission according to claim 1, further comprising bearings for supporting the layshafts, at least one of the bearings being provided next to each of the pinions.
 10. The double-clutch transmission according to claim 9, wherein at least one of the bearings is provided next to one of the idler gearwheels of low gears.
 11. A gearbox, comprising; an inner input shaft and an outer input shaft, at least a portion of the inner input shaft surrounded by the outer input shaft; a first clutch connected to the inner input shaft and a second clutch connected to the outer input shaft; a first layshaft, a second layshaft and a third layshaft spaced apart from the input shafts and arranged in parallel to the input shafts; at least one of the layshafts comprising a pinion for outputting a drive torque; gearwheels arranged on the first layshaft, on the second layshaft, on the third layshaft, on the inner input shaft and on the outer input shaft, the gearwheels comprising a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group, a sixth gearwheel group and a seventh gearwheel group for providing seven sequentially increasing gears, the first gearwheel group comprising a first fixed gearwheel on the inner input shaft, meshing with a first gear idler gearwheel on one of the layshafts, the third gearwheel group comprising a third driving gearwheel on the inner input shaft, meshing with a third driven gearwheel on one of the layshafts, the fifth gearwheel group comprising a fifth fixed gearwheel on the inner input shaft, meshing with a fifth gear idler gearwheel on one of the layshafts, the seventh gearwheel group comprising a seventh fixed gearwheel on the inner input shaft, meshing with a seventh gear idler gearwheel on one of the layshafts, the second gearwheel group comprising a second fixed gearwheel on the outer input shafts, meshing with a second gear idler gearwheel on one of the layshafts, the fourth gearwheel group comprising a fourth fixed gearwheel on the outer input shafts, meshing with a fourth gear idler gearwheel on one of the layshafts, the sixth gearwheel group comprising a sixth fixed gearwheel on the outer input shafts, meshing with a sixth gear idler gearwheel on one of the layshafts, and each gearwheel group comprising a coupling device which is arranged on one of the layshaft to selectively engage one of the gearwheels for selecting one of the seven gears, and the fourth fixed gearwheel further meshing with the sixth gear idler gearwheel, wherein the fifth fixed gearwheel further meshes with the seventh gear idler gearwheel, and the gearwheels further comprises a reverse gearwheel group that comprises a fixed gearwheel on one of the input shafts, meshing with a reverse gear idler gearwheel on one of the layshafts for providing a reverse gear, and the reverse gearwheel group further comprises a coupling device which is arranged on the layshaft mounted with the reverse gear idler gearwheel to selectively engage the reverse gear idler gearwheel; and an output gearwheel on an output shaft, the output gearwheel meshing with the pinions.
 12. A power train device, comprising: an inner input shaft and an outer input shaft, at least a portion of the inner input shaft surrounded by the outer input shaft; a first clutch connected to the inner input shaft and a second clutch connected to the outer input shaft; a first layshaft, a second layshaft and a third layshaft spaced apart from the input shafts and arranged in parallel to the input shafts; at least one of the layshafts comprising a pinion for outputting a drive torque; gearwheels arranged on the first layshaft, on the second layshaft, on the third layshaft, on the inner input shaft and on the outer input shaft, the gearwheels comprising a first gearwheel group, a second gearwheel group, a third gearwheel group, a fourth gearwheel group, a fifth gearwheel group, a sixth gearwheel group and a seventh gearwheel group for providing seven sequentially increasing gears, the first gearwheel group comprising a first fixed gearwheel on the inner input shaft, meshing with a first gear idler gearwheel on one of the layshafts, the third gearwheel group comprising a third driving gearwheel on the inner input shaft, meshing with a third driven gearwheel on one of the layshafts, the fifth gearwheel group comprising a fifth fixed gearwheel on the inner input shaft, meshing with a fifth gear idler gearwheel on one of the layshafts, the seventh gearwheel group comprising a seventh fixed gearwheel on the inner input shaft, meshing with a seventh gear idler gearwheel on one of the layshafts, the second gearwheel group comprising a second fixed gearwheel on the outer input shafts, meshing with a second gear idler gearwheel on one of the layshafts, the fourth gearwheel group comprising a fourth fixed gearwheel on the outer input shafts, meshing with a fourth gear idler gearwheel on one of the layshafts, the sixth gearwheel group comprising a sixth fixed gearwheel on the outer input shafts, meshing with a sixth gear idler gearwheel on one of the layshafts, and each gearwheel group comprising a coupling device which is arranged on one of the layshaft to selectively engage one of the gearwheels for selecting one of the seven gears, and the fourth fixed gearwheel further meshing with the sixth gear idler gearwheel, wherein the fifth fixed gearwheel further meshes with the seventh gear idler gearwheel, and the gearwheels further comprises a reverse gearwheel group that comprises a fixed gearwheel on one of the input shafts, meshing with a reverse gear idler gearwheel on one of the layshafts for providing a reverse gear, and the reverse gearwheel group further comprises a coupling device which is arranged on the layshaft mounted with the reverse gear idler gearwheel to selectively engage the reverse gear idler gearwheel; an output gearwheel on an output shaft, the output gearwheel meshing with the pinions; and at least one power source for generating a driving torque.
 13. The power train device according to claim 12, wherein the power source comprises a combustion engine.
 14. The power train device of claim 12, wherein the power source comprises an electric motor.
 15. (canceled) 